Lookahead Noise Intervention Optimization (LNIO): Fourth Experimental Report — Evaluating Penalized Top-1 Lookahead Selection Across E8, E4, and E2 Decision Intervals

This fourth experimental report investigates the effect of penalized Top-1 selection within Lookahead Noise Intervention Optimization (LNIO), focusing on three decision intervals: E8, E4, and E2. The experiment evaluates 29 sampling configurations using Stable Diffusion 1.5, with 20 prompts, two random seeds, and 40 conditions per method, resulting in 1,160 method-condition evaluations. ImageReward is used as the primary evaluation metric, while CLIP similarity serves as a supplementary metric. The central experimental question is whether a lookahead mechanism that identifies the highest-ranked preview candidate but deliberately reduces its selection probability can produce favorable downstream generation outcomes. The results show that all three Penalized Top-1 configurations—E8, E4, and E2—rank within the top five methods by mean ImageReward. E8 Penalized Top-1 obtains the highest mean ImageReward across all 29 configurations (−0.1674), followed closely by the adaptive baseline (−0.1678). E4 and E2 Penalized Top-1 rank fourth (−0.1894) and fifth (−0.1941), respectively. However, paired statistical tests with Holm correction do not establish statistically significant differences among the tested configurations. The results therefore provide encouraging descriptive evidence for penalized Top-1 lookahead selection, while also highlighting the need for larger-scale validation and more independent evaluation.